Electroencephalography (EEG) is the recording of the electrical activity of the brain by detecting, i.e. acquiring, the electric potential associated with the currents flowing on the cerebral cortex. Electroencephalography is a non-invasive investigation means having a fundamental importance for the study of the physiology and pathophysiology of nervous centers. EEG is very useful in the differential diagnosis between epileptic and non-epileptic seizures and contributes to the definition of the nature of the crisis and/or epileptic syndrome.
It is known that the registration of a electroencephalographic signal is carried out by applying at different points of the head of a patient two or more electrodes, a “bias” electrode, as well as a reference electrode. These electrodes are held together e.g. by way of an elastic cap and are applied on the scalp of the patient at pre-established positions according to different standards. The standard positioning system known as “International System 10/20” is particularly widespread due to its simplicity of use and effectiveness. The “International System 10/20” exploits as skull landmarks the craniometric point “inion”, i.e. the most prominent point at the back of the head, and the craniometric point “nasion”, i.e. where the top of the nose meets the ridge of the forehead. According to this standard, frontal polar electrodes are placed above the eyebrows at the 10% of the inion-nasion distance, frontal electrodes are placed on the same line of the frontal polar electrodes but at the 20% of the inion-nasion distance, and, with respect to the latter, central, parietal and occipital electrodes are positioned at a respective distance progressively greater than 20%.
Electroencephalography applications are numerous and include the study of sleeping disorders such as apnea, dyssomnia (insomnia, hypersomnia, narcolepsy) and parasomnia (bruxism, bedwetting, night terror, sleep walking), detection of brain death, which is characterized by a flat EEG record, and detection of alterations caused by abscesses, calcifications, cysts, hematomas, bleeding, inflammation, malformations or benign or malignant tumors of the brain.
Electroencephalography is employed as an aid in the diagnosis of senile dementia and neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease. It also represents a monitoring tool for the neuromotor apparatus in the evaluation of cognitive and motor recovery at the level of the central nervous system.
Electroencephalography is increasingly being used in the diagnosis and monitoring of seizure disorders such as epilepsy.
Epilepsy is a chronic neurological disorder that affects millions of people worldwide. It is characterized by recurrent seizures caused by abnormal activity of brain nerve cells. Seizures can occur as attention loss, fainting, convulsion and, when they are frequent there is a risk of personal injury up to death. An accurate diagnosis of epilepsy is crucial and requires several tests, including electroencephalography, which is even considered necessary and indispensable.
EEG monitoring of patients with epilepsy are typically performed in hospitals and specialized centers by placing a patient on a bed and connecting individual electrodes placed on the patient's head to a fixed EEG device provided with data processing units through wires.
In order to carry out diagnoses and management of patients with suspected or already established epilepsy traditional electroencephalograms are typically recorded also known as “Standard EEG”, as well as dynamic electroencephalograms of a longer duration, such as 24 hours, known as “Holter EEG” or “Ambulatory EEG”.
Also known are the so-called “Video-EEG” monitoring systems, according to which an epileptic patient is video recorded for a short or a long time while subjected to an electroencephalographic monitoring. Video-EEG monitoring is carried out in a hospital in a specific hospital room equipped with a closed circuit television system configured for both the daytime and nighttime recording. There is an increasing scientific interest in Video-EEG systems, because they allow to correlate EEG records with actual images of a patient, thus making it possible to analyze clinical data (myoclonic events, avert eyes, absences and the like) related to abnormalities detected by the EEG and hence to make differential diagnoses between epileptic and non-epileptic episodes, to improve the definition of the specific epileptic syndrome, as well as to quantify the crisis anomalies and to study sleeping disorders. Thanks to the possibility of relate EEG and images of a patient, the time required for a diagnosis can be greatly reduced.
Traditional electroencephalography is a long and uncomfortable examination for a patient and particularly for a pediatric patient, because of the time required for the positioning and connection of the electrodes to the acquisition system, and due to the duration of the recordings, which is typically between 20 and 40 minutes, but can also be longer, for example of the order of days, in the case of epilepsy since it is substantially impossibility to predict the onset of a crisis.
In the specific case of Video-EEG monitoring a patient must stay in a bed, sitting or lying thereon assisted by an attendant with the additional constraint of having to keep a position well-framed by the cameras.
For dynamic or long-term EEG monitoring EEG portable devices configured to be worn by a patient are also known. These devices are configured like helmets and are equipped with a plurality of electrodes typically arranged according to the international standard 10/20. These helmets comprise a plurality of interconnected portions whose relative position is adjustable depending on the size of the patient's head. Bioelectric signals acquired through the electrodes can be transmitted to an electronic unit associated with the EEG device, e.g. mounted on a portion of the helmet, or to a remote electronic unit connected to the EEG device through wires or in a wireless mode.
The electrodes may be of a wet type, according to which the electrical contact with a patient's scalp is obtained indirectly through a conductive gel, or of a dry type, according to which the electrical contact with a patient's scalp is direct and requires a slight compression of an electrode on the scalp so as to penetrate through the hair and ensure a proper detection of the bioelectric signals. Dry-type electrodes are typically provided with a plurality of contact arms that contact a portion of the scalp at several points and can thus ensure an adequate electrical contact because they fit more easily through the hair.
Dynamic monitoring with portable EEG devices (Holter EEG) is considered more effective than monitoring with fixed EEG equipment, because it allows to perform monitoring either in a hospital or at home, where a patient generally has a more natural and relaxed attitude, which increases the probability of recording seizures, or more in general occurrence of the disorders to be investigated within a given time period. EEG monitoring at home is also a much less expensive than hospitalization in a specialized center and is therefore more sustainable for the public health.
A portable EEG device of the aforementioned type comprising wet electrodes is e.g. disclosed in the patent publication EP 2762069 A1.
Dry electrodes for use in EEG devices are for example disclosed in the international publication WO 2013/142316 A1.
In both cases, the electrodes have elastically deformable structures and/or means suitable to facilitate their positioning on a patient's head and to minimize the physical pain they bring during prolonged monitoring periods.
Also known are Video-EEG systems comprising a portable EEG device combined with a camera system such as a web-cam connected to a computer, allowing to carry out video monitoring at home, although in a less accurate way compared to a video monitoring carried out by way of a hospital equipment.
An example of a Video-EEG system is disclosed by the patent publication US 2014/051044 A1, which corresponds to the preamble of the independent claim 1.
Despite the availability of many types of portable devices for electroencephalography and video electroencephalography, there still exists the need to find improved devices particularly aimed at long-term monitoring of patients suffering from epilepsy, as well as at epilepsy diagnoses, which is an object of the present invention. Said object is achieved with a portable device for video electroencephalography, whose main features are specified in the first claim, while other features are specified in the remaining claims.